NOISE ATTENUATING WALL

Abstract: The present invention relates to a noise screen adapted to keep down the sound from one side which is characteristic in that the vertical cross section of the noise screen (1) is zigzag-shaped, alternating between absorbing faces (2) and reflecting faces (3), and that the absorbing faces (2) are arranged on the faces tilting upwards towards the sound side. The reflecting faces (3) are preferably transparent for providing an esthetic appearance of the noise screen, but may also be non-transparent for excluding road-users from viewing inhabited areas behind the noise screen (1). The reflecting faces (3) may also in the height as well as the length of the noise screen (1) alternate between being transparent and non-transparent. The noise screen (1) is built up in modules which are placed on posts (8) which seen in cross section may be compressed respectively extended telescopically in the longitudinal direction of the noise screen (1).

Description: NOISE ATTENUATING WALL The present invention relates to a noise screen adapted to keep down the sound from one side. Noise screens are generally modular, vertical screens for use in connection with screening and/or absorption of noise/sound coming from outside by traffic installations and work places. It is particularly important that noise screens are soundproof in vertical as well as horizontal direction since any aperture in a noise screen will be pen¬ etrated by the noise. Noise screens are known to appear in several embodiments for outdoor and indoor use in that any tight structure of materials with a weight of over 20 kg/m 2 has a good screen¬ ing effect. Noise absorbing screens are also known in several embodi- ments, for example built up as described in utility model specification DK 93 000 58 U3. Furthermore, transparent screens are known in embodiments which are screening noise without being absorbing, as de- scribed in utility model specification DK 93 00299 U3. Known noise screens are disadvantageous in that the ver¬ tical screen reflects the noise, for example to residents living on the opposite side of the noise source. However, absorbing screens are known but these screens are disadvantageous in that due to the absorption material it is difficult to make them transparent and thereby they ob¬ struct the view of the residents who are to be protected against a noise source. It is therefore the object of the present invention to pro¬ vide a noise screen which, apart from screening the area behind the noise screen from noise/sound, will also absorb the noise and thereby reduce reflections from the noise screen to the area in front of the noise screen. This object is achieved by a noise screen of the type re¬ cited in the introduction, said noise screen according to the invention being characteristic in that the vertical cross section of the noise screen is zigzag-shaped, altern¬ ating between absorbing faces and reflecting faces, and that the absorbing faces are arranged on the faces tilting upwards towards the sound side. Noise, such as noise from work, wheels and traffic, which is to be screened by means of noise screens, is usually emitted from a low height and spreads in a ball-shaped fashion in all directions. When the absorbing screens ac¬ cording to the invention tilt upwards, the absorbing faces thereof will essentially face the noise source and there¬ fore absorb the greater part of same. The noise, which hits the reflecting faces, will be reflected towards the absorb¬ ing faces so that a substantial amount of the emitted noise is absorbed by the absorbing faces. Accordingly, by the noise screen according to the invention there is achieved a substantial improvement of the acoustic properties thereof relative to the known noise screens. When the reflecting faces are tilted, there is no risk either that they will reflect light from headlights of cars which might cause substantial inconvenience to traffic safety. Advantageously, the reflecting faces are transparent and therefore provide a high degree of transmitted light, which benefits the residents living behind the noise screen so that they will not feel locked up behind a tight screen, and also assists the orientation of the road-users emitting the noise. The transparent faces also break any feeling of the road-users of driving inside a tunnel when a noise screen of the described kind has been erected on either side of the road. In other cases, however, it is advantageous that the re- fleeting faces are non-transparent in view of the privacy of the residents behind the noise screen. Finally, it is advantageous that the reflecting faces in the height of the noise screen as well as along its length alternate in an arbitrary pattern between transparent and non-transparent faces so that it is possible to break the appearance of the noise screen, which might appear monoton¬ ous by a long noise screen. From an architectural point of view it is advantageous that the noise screen terminates with a transparent, reflecting face at its upper end in that the noise screen will thus provide an impression of being lower than the true height and additionally contribute to an esthetic appearance of the noise screen. The absorbing faces may curve in an outward direction to¬ wards the noise source. The absorbing faces comprise a substantially U-shaped rear plate, when seen in cross section, and a sound absorbing material arranged on the side facing the noise source, said material being kept in place by a perforated protective plate which, also seen in cross section, is substantially U-shaped, where the two U-shaped plates are mutually inter¬ locking with the U-legs facing each other in that the upper U-leg of the rear plate in the position of use rests inside the adjacent U-leg of the protective plate, and the lower U-leg of the rear plate rests outside the adjacent U-leg of the protective plate. By a preferred embodiment the rear plate at the upper lon¬ gitudinal edge in the position of use is bent approx. 90° twice such that the end extends back towards the lower lon¬ gitudinal edge substantially parallelly to the plane of the rear plate at a distance thereof, and the lower longitud¬ inal edge is bent to form an angle the size of which de¬ pends on the tilt of the absorbing faces in the noise screen in that this lower bent end is to point down towards the upper longitudinal edge of the absorbing face placed below. By this preferred embodiment the perforated protective plate at the lower longitudinal edge in the position of use is bent twice, the first time approx. 90°, and the second time at an angle which is somewhat bigger than 90°, the size of said latter angle depending on the tilt of the ab¬ sorbing faces in the noise screen in that the section be¬ tween the two bendings in the mounted position is to extend parallelly to the lower bent end of the rear plate, and at the upper longitudinal edge the protective plate is bent at an angle which is smaller than 90°. The noise screen according to the invention is in a manner known per se built up by modules secured to vertical posts which are mounted in bases buried in the ground. For tightness along the noise screen the modules are fixedly secured to the posts, and it is therefore necessary to com¬ pensate for the changes in the length of the individual modules which are caused by temperature variations during night and day and the year. The modules for the noise screen according to the invention are therefore mounted on posts which, seen in cross sec¬ tion, may be compressed respectively extended telescopic- ally in the longitudinal direction of the noise screen. In this connection the posts advantageously consist of two equally sized and congruent post profiles. When the post profiles are equally sized and congruent, they may advantageously be bent from plate in such a manner that either of the post profiles has a plane face at right angles to the longitudinal direction of the noise screen, that at the first side edge of the plane face the post pro¬ file is bent approx. 90° twice such that the end extends back towards the opposite side edge of the post profile substantially parallelly to the plane face and at a dis¬ tance thereof, and that apart from the said two bendings of the first side edge, the opposite second side edge is bent one more time such that the free edge extends away from the plane face substantially at right angles thereto. The noise screen according to the invention will be further explained in the following detailed description with refer¬ ence to the drawing wherein fig. 1 is a vertical cross section of a first embodiment of a noise screen according to the invention where the reflecting faces are transparent and the ab¬ sorbing faces are plane, fig. 2 is a cross section of an absorbing face for a noise screen according to the invention shown at a larger scale, fig. 3 is a vertical cross section of a second embodiment of a noise screen according to the invention where the reflecting faces are non-transparent and the absorbing faces are plane, fig. 4 is a vertical cross section of a third embodiment of a noise screen according to the invention where the reflecting faces are alternately transparent and non-transparent, and the absorbing faces curve in an outward direction towards the noise source, fig. 5 is a vertical cross section of a fourth embodiment of a noise screen according to the invention where the reflecting faces extend upwards in a rearward direction relative to horizontal at a greater angle than 45°, whereas the absorbing faces tilt 45°, and fig. 6 is a horizontal cross section of a post for mount¬ ing a module for a noise screen according to the invention, said post consisting of two equally sized and congruent post profiles. Reference is first made to fig. 1 showing a vertical sec¬ tion of a module for a noise screen 1 according to the in¬ vention. The module is built up by absorbing faces 2 al- ternating with reflecting, transparent faces 3 in such a manner that the faces 2, 3 extend mutually upwards in a zigzag-shape. Each of the absorbing faces 2 tilt upwards and outwards in a direction towards the sound side. By means of the transparent faces 3 it is possible to ac¬ quaint oneself with what is happening behind the noise screen, which may have implications for orientation and lighting. Reference is now made to fig. 2. The absorbing faces 2 are shaped by a rigid rear plate 2a, which on the side facing the noise source is provided with a sound absorbing mater¬ ial 2b which is kept in place by a perforated protective plate 2c. The rigid rear plate 2a is bent from a plane plate which at the upper longitudinal edge in the position of use is bent approx. 90° twice so that the end extends back towards the lower longitudinal edge substantially parallelly to the plane of the rear plate at a distance thereof. Sub¬ sequently, the lower longitudinal edge is bent to form an angle, the size of which is smaller that 90° and depends on the tilt of the absorbing faces 2 in the noise screen in that said lower bent edge is to point down towards the up- per longitudinal edge of the absorbing face 2 placed below. The perforated protective plate 2c is bent twice at the lower longitudinal edge in the position of use, the first time approx. 90°, and the next time at an angle the size of which depends on the tilt of the absorbing faces 2 in the noise screen in that the section between the two bendings in the mounted position is to extend parallelly to the lower bent edge of the rear plate 2a. At the upper longit¬ udinal edge, the protective plate 2c is bent at an angle which is smaller than 90°. When the protective plate 2c is mounted on the rear plate 2a, as shown in fig. 2, there is formed at the longitudinal edges thereof a slot or groove 4a and 4b, respectively, facing in opposite directions, in that the groove 4a has its opening downwards towards the sound side and is limited by two substantially parallel walls, and the opening of the groove 4b diverges upwards and away from the sound side. By the described embodiment of the rear plate 2a and the protective plate 2c it is possible to secure the protective plate 2c to the rear plate 2a by means of a single screw 5 at either end of the protective plate 2c. It is thereby possible to mount and remove arbitrary faces 2 and/or 3 in the noise screen in case this should become necessary for reasons of maintenance. The absorbing faces 2, 2', 2' ', ..., and the reflecting faces 3, 3', 3' ', ..., may by means of the grooves 4a, 4b be tightly connected by their longitudinal edges when a re- fleeting face 3 placed above is introduced with one of its longitudinal edges into the groove 4b in the absorbing face 2 placed below, and the opposite second longitudinal edge of the reflecting face 3 is made to rest in the bent lon¬ gitudinal edge of the absorbing face 2' placed above, whereafter the subsequent protective plate 2c' is mounted with the screw 5 and so on in an upwards direction. This embodiment provides for the highly important tightness of a noise screen between the absorbing faces 2 and the re- fleeting faces 3, in that, if so required, this tightness may be improved for example by placing sealings of rubber or a similar material in the grooves 4a and 4b. The sound absorbing material 2b must be a weather-resistant material which will not absorb moisture, for example 30 mm mineral wool. The rigid rear plate 2a must be of a weather-resistant ma¬ terial, for example 3 mm hot-galvanised plate, whereas the protective plate 2c for example consists of 3 mm 60% per¬ forated, hot-galvanised plate. The reflecting and transparent faces 3 consist for example of 8 mm hardened glass or a corresponding plastic material. By the end edges the absorbing faces 2 are bent to form end walls 6 extending substantially at right angles to the plane rear plate 2a. The end walls 6 are provided with holes 7 for screws or similar retaining means such that the absorbing faces 2 may be tightly connected to posts 8 placed at either end of a module to support same. The acoustic tightness between the posts 8 and the end walls 6 will be improved by placing sealings between the surfaces of contact. The absorbing faces 2 and the reflecting faces 3 are se- cured to the posts 8 in such a manner that they tilt 45° relative to the horizontal plane. At the lower end, the noise screen 1 according to the in¬ vention is terminated close to the ground by means of a base unit 10 serving as a bottom reflecting face and made, for example, of hot-galvanised plate which by a longitud¬ inal bend is divided into an upper part, which in the posi¬ tion of use must have the same tilt as the reflecting face 2 placed above, and a lower part, which is intended for being dug into the ground. Reference is now being made to fig. 3 showing a second em¬ bodiment in that the reflecting faces 3 are not transpar¬ ent, but opaque, such that the area behind the noise screen cannot be seen and is protected against incident light. The reflecting faces 3 in question consist, for example, of hot-galvanised plate or a plate of plastic which can be coloured by suitable dyes. Fig. 4 shows a cross section of a third embodiment of a noise screen according to the invention. This embodiment differs from the embodiments shown in figs. 1 and 3 in that transparent as well as non-transparent reflecting faces 3 are used. It should be noted that the transparent and non- transparent faces 3 are not necessarily arranged altern- ately in the noise screen according to the invention. There may accordingly below and above a given absorbing face 2 be arranged a transparent face 3 whereafter there is arranged a non-transparent face 3 after the next or the following absorbing faces 2. It should also be mentioned that the pattern of arrangement of the transparent and non-transparent faces 3 according to the invention may vary from one module to the other in a noise screen 1 according to the invention. It will be seen that the sound absorbing material 2b and the protective plates 2c curve outwards towards the sound side and this embodiment is also applicable in the embodi¬ ments shown in figs. 1 and 3. Fig. 5 shows an embodiment wherein the reflecting faces 3 tilt upwards in a rearward direction relative to horizontal at a greater angle than 45°, for example 60°. It will be understood that also the tilt of the absorbing faces 2 may optionally depart from the shown angles and that the tilt of the absorbing faces 2 as well as the reflecting faces 3 may even vary upwards along the noise screen according to the invention. The modules for the noise screen 1 according to the inven¬ tion are mounted as stated above on posts 8 shown in a ho¬ rizontal cross section in fig. 6. Since the posts must be capable of absorbing variations in length of the modules, each of the posts is made in such a manner that it may ex¬ tend respectively contract telescopically in the longitud¬ inal direction of the noise screen. To achieve this purpose the posts are built up by two parts 8a which are mutually kept together by bolts 9 (see figs. 1, 3, 4 and 6) which must be secured to the post profiles 8a in such a manner that the two profiles may freely adjust themselves in the longitudinal direction of the noise screen. The posts 8 are secured by means of bolts to piles or bases, for example of concrete or a similar material which can be cast in the ground, as indicated in figs. 1, 3, 4 and 5. The two parts 8a of the posts 8 are advantageously designed as two equally sized and congruent post profiles whereby the manufacture of the posts may be simplified and storage space may be saved. Each post profile 8a has a plane face at right angles to the longitudinal direction of the noise screen, and at the first side edge of the plane face the post profile 8a is bent approx. 90° twice such that the end extends back to¬ wards the opposite side edge of the post profile substan- tially parallelly to the plane face and at a distance thereof. Apart from the said two bendings of the first side edge, the opposite second side edge is bent one more time such that the free edge extends away from the plane face substantially at right angles thereto. With a view to blurring the posts as much as possible these are provided with holes 11 permitting fastening of planting wire which may form an espalier for plants, which may be planted against the noise screen.

Claims: P A T E N T C L A I M S 1. Noise screen adapted to keep down the sound from one side, characterised in that the vertical cross section of the noise screen (1) is zigzag-shaped, alternating between absorbing faces (2) and reflecting faces (3) , and that the absorbing faces (2) are arranged on the faces tilting up¬ wards towards the sound side. 2. Noise screen according to claim 1, characterised in that the reflecting faces (3) are transparent. 3. Noise screen according to claim 1, characterised in that the reflecting faces (3) are non-transparent. 4. Noise screen according to claim 1, characterised in that in the height of the noise screen (1) as well as along its length the reflecting faces (3) alternate in an arbit¬ rary pattern between transparent and non-transparent faces. 5. Noise screen according to claim 2 or 4, characterised in that at its upper end the noise screen (1) terminates with a reflecting, transparent face (3). 6. Noise screen according to claim 1, 2, 3, 4 or 5, char¬ acterised in that the absorbing faces (2) curve in an out¬ ward direction towards the sound side. 7. Noise screen according to claim 1, 2, 3, 4, 5 or 6, characterised in that the absorbing faces (2) and the re¬ flecting faces (3) tilt 45° relative to the horizontal plane. 8. Noise screen according to claim 1, 2, 3, 4, 5 or 6, characterised in that the reflecting faces (3) extend up¬ wards in a rearward direction relative to the horizontal plane at a greater angle than 45°, for example 60°. 9. Noise screen according to any one of claims 1-8, char¬ acterised in that seen in cross section the absorbing faces (2) comprise a substantially U-shaped rear plate (2a) and a sound absorbing material (2b) arranged on the side facing the noise source, said material (2b) being kept in place by a perforated protective plate (2c) which, also seen in cross section, is substantially U-shaped, where the two U- shaped plates (2a, 2c) are mutually interlocking with the U-legs facing each other in that the upper U-leg of the rear plate (2a) in the position of use rests inside the ad¬ jacent U-leg of the protective plate (2c) and the lower U- leg of the rear plate (2a) rests outside the adjacent U-leg of the protective plate (2c). 10. Noise screen according to claim 9, characterised in that at the upper longitudinal edge in the position of use the rear plate (2a) is bent approx. 90° twice such that the end extends back towards the lower longitudinal edge sub¬ stantially parallelly to the plane of the rear plate (2a) at a distance thereof, and that the lower longitudinal edge is bent to form an angle the size of which depends on the tilt of the absorbing faces (2) in the noise screen in that this lower bent end is to point down towards the upper lon¬ gitudinal edge of the absorbing face (2) placed below. 11. Noise screen according to claim 10, characterised in that at the lower longitudinal edge in the position of use the perforated protective plate (2c) is bent twice, the first time approx. 90°, and the next time at an angle which is somewhat bigger than 90°, the size of said latter angle depending on the tilt of the absorbing faces (2) in the noise screen (1) in that the section between the two bend- ings in the mounted position is to extend parallelly to the lower bent end of the rear plate (2a), and that at the up- per longitudinal edge the protective plate (2c) is bent at an angle which is smaller than 90°. 12. Noise screen according to one of the preceeding claims, characterised in that the posts (8) for the noise screen (1) seen in cross section may be compressed respectively extended telescopically in the longitudinal direction of the noise screen (1). 13. Noise screen according to claim 12, characterised in that seen in cross section the posts (8) consist of two equally sized and congruent post profiles (8a). 14. Noise screen according to claim 12 or 13, characterised in that either of the post profiles (8a) has a plane face at right angles to the longitudinal direction of the noise screen (1), that at the first side edge of the plane face the post profile (8a) is bent approx. 90° twice such that the end extends back towards the opposite side edge of the post profile substantially parallelly to the plane face and at a distance thereof, and that apart from the said two bendings of the first side edge, the opposite second side edge is bent one more time such that the free edge extends away from the plane face substantially at right angles thereto.

Inventors: NIELSEN CLAUS, NIELSEN, CLAUS
Applicants: NIELSEN CLAUS, PLINIUS ERIK, NIELSEN, CLAUS, PLINIUS, ERIK
Application year: 1994
Main classification: E01F8
IPC codes: E01F8